Heavy-duty machine elements which are subjected to high loads or stresses have hitherto been formed as forgings from high-cost nickel-content alloys which in themselves are very expensive and which consequently cause such machine element made therefrom to be likewise very expensive. Nevertheless, in such machine elements only a portion thereof is ordinarily subjected to concentrated heavy loads, torques or stresses which require the use of high performance alloys, yet the formation of the entire machine element from such high performance alloys has hitherto been necessitated, requiring high cost forging operations in its production.
The present invention overcomes these prior disadvantages by providng heavy-duty machine elements wherein the working portions subjected to heavy or concentrated loads, torques or other stresses are formed from sintered powdered high-performance alloys whereas the remaining portions not so loaded are formed from sintered powdered low-performance metals. The two portions are bonded to one another inseparably as a result of their being sintered together. As a result, the quantity of high-cost, high-performance alloy in each machine element is greatly reduced in comparison with the same machine element forged from solid high-performance alloy throughout, with a corresponding reduction in the ultimate cost of the finished machine element as wel as a conservation of nickel and other expensive metals. At the same time, the heavy-duty performance capability of the composite machine element is preserved without entailing the high cost previously accompanying the production of forged unitary high-performance machine elements. Moreover, test specimens made according to this invention and subjected to tensile strength tests in tension testing machines show that rupture of such specimens occurs at locations spaced away from the junctions between the two metals and not at such junctions.